What a deep foundation is
A foundation is deep when it transmits the building’s loads to ground strata located at considerable depth, because the shallower ones lack the necessary bearing capacity. This is usually done with piles: long elements of reinforced concrete, steel or other materials, either driven into the ground or bored and cast in place.
The piles are joined at the head by pile caps, on which the structure rests.
When piles are used
The decision is driven by the geotechnical survey. A deep foundation is usually needed when:
- The surface soil is soft or consists of fill and lacks sufficient bearing capacity.
- The settlements expected with a shallow foundation would be excessive.
- The structural loads are very high.
- There are expansive clays, a high water table or other conditions that make a shallow foundation inadvisable.
Before opting for piles, the ground should be studied thoroughly: in some cases, well-designed shallow solutions can solve the problem. We assess this in our foundations service.
Why it is an aggravating factor for decennial insurance
Piling is a highly specialised technique requiring specific machinery, so it is usually entrusted to specialist firms. Moreover, once built, piles are buried and their quality cannot be checked by eye.
That is why insurers regard deep foundations as an aggravated risk when issuing decennial insurance. This is reflected in higher premiums or even a refusal to provide cover unless proper supervision of the construction is guaranteed.
How construction is controlled
To insure the works, technical control pays particular attention to deep foundations. The Technical Control Body (OCT) issues a specific report on special work units, covering piles, diaphragm walls, expansive clays and sloping ground.
During construction, checks include, among other things:
- That the depth and embedment of each pile in the bearing stratum match the design.
- The reinforcement and concreting.
- Integrity tests on the completed piles.
- That the pile caps and the connection to the structure are correct.
How we help you
At Grupo Octplus we specialise in special foundations:
- At Ingeniería Estructural Plus we design and calculate the deep foundation, or the alternative best suited to your ground.
- OCTPLUS, as a Technical Control Body, supervises its construction so that insurers can rely on the works.
Important. This guide is for general information only: the foundation solution for each project depends on its geotechnical survey and its design.